1. Field of the Invention
This invention relates to an improved process for transfer printing onto solid objects (substrates) made of plastic or objects having a plastic surface coating, e.g., varnish. More specifically, the transfer printing is effected more efficiently during the dye transfer by the sheet dye carrier being pressed to the surface to be printed by super atmospheric gas pressure while the surface is kept at a temperature below the thermoplastic range of the plastic or plastic coating.
2. Description of the Prior Art
In the past, transfer printing, which is most commonly used in the fabric industry, has typically involved the process whereby a sublimable dye is tranferred to the surface to be printed using a sheet dye carrier at an elevated temperature. During the transfer, the dye carrier is pressed onto the surface of the object to be printed.
Transfer printing onto varnished surfaces of solid objects such as sheet metal strips is described in DE-A No. 29 14 704. The transfer printing takes place through the passage of the varnished metal and a transfer printing paper over a calander. ln accordance with the process described in DE-A No. 26 42 350, the transfer printing along with the coating of a solid object is summarized as a process in which a thermoplastic plastic foil is laminated onto the surface of a solid object while a dye is transferred to the synthetic layer from a dye carrier. Various standard processes can be used for the lamination, such as high-frequency or ultrasound lamination or hot air sealing. Since the lamination and dye transfer take place while the coating is in a thermoplastic state, the original shine of the plastic surface is not maintained in that process.
It is highly desirable that the surface shine is maintained during transfer printing onto objects made of plastic or having a plastic surface coating such as varnish. Such a process is not found in the prior art.